Learn Hardcore German: Wir halten uns an die Regel.

If you say Wir halten an die Regel, it sounds wrong to a native speaker; it feels like something is missing. It would be understood, if at all, as We stop at the rule (confused with anhalten = to stop) rather than We stick to the rule.

So you must include the reflexive pronoun: Wir halten uns an die Regel.

What exactly does sich an etwas halten mean compared to the basic verb halten?

The basic verb halten is very physical:

Ich halte das Buch. – I hold the book.
Halt das fest! – Hold that tight!

With the reflexive + preposition, sich an etwas halten becomes idiomatic and means:

to stick to something
to follow / to abide by something
typically: rules, plans, agreements, schedules

Examples:

Wir halten uns an die Regel. – We stick to the rule.
Bitte haltet euch an den Plan. – Please stick to the plan.
Sie halten sich nicht an die Abmachung. – They are not keeping to the agreement.

So sich an etwas halten is not about physically holding, but about orienting your behavior according to something (rules, plan, etc.).

Why is it an die Regel and not an der Regel?

An is a so‑called two-way preposition. It can take:

dative: when it’s about location (Wo? – where?)
accusative: when it’s about direction or targeted orientation (Wohin? – where to? / toward what?)

With sich an etwas halten, German treats it like an orientation toward something, so it always uses accusative:

sich an die Regel halten
sich an den Plan halten
sich an das Gesetz halten

So die Regel here is accusative feminine singular. Feminine nouns use die for both nominative and accusative, so you see it’s accusative because of the verb + preposition pattern (sich an + Akk. halten), not from the article form itself.

An der Regel (dative) would not be used in this expression.

What case is die Regel in, and how can I tell?

Grammatically, die Regel here is:

Accusative
Feminine
Singular

How to tell:

The verb–preposition combination
The expression is sich an etwas halten, and in this idiom an always takes the accusative.
Feminine article forms
For feminine nouns, nominative and accusative are both die:

Nominative: die Regel
Accusative: die Regel

So the form die itself does not distinguish nominative from accusative with feminine nouns. You know it’s accusative because it’s the object of “an” in this fixed phrase.

Could I use other prepositions like nach, zu, or auf instead of an?

Not with this meaning.

For stick to / follow / abide by a rule, the idiomatic options are:

sich an eine Regel halten – to stick to a rule
eine Regel befolgen – to follow a rule
eine Regel einhalten – to comply with / observe a rule

Using other prepositions changes or destroys the meaning:

Wir halten uns nach der Regel. – wrong/unnatural in this meaning.
Wir halten uns zu der Regel. – wrong/unnatural here.
Wir halten uns auf die Regel. – wrong/unnatural.

So for this structure you should memorize:
sich an + Akkusativ halten for rules, plans, agreements, etc.

How does Wir halten uns an die Regel differ from Wir befolgen die Regel or Wir halten die Regel ein?

All three can describe following a rule, but there are nuances:

Wir halten uns an die Regel.
- Very common in spoken German.
- Slightly more colloquial / neutral.
- Focus: our behavior being oriented toward the rule.
Wir befolgen die Regel.
- Sounds a bit more formal and “legal/official”.
- Common in written texts, instructions, or regulations.
- More like We obey the rule.
Wir halten die Regel ein.
- Also quite common, including in official contexts.
- Focus on fulfilling / complying with a rule or deadline.
- Can also be used more broadly: eine Frist einhalten (keep a deadline), einen Termin einhalten (keep an appointment).

All are correct; often they’re interchangeable, but sich an die Regel halten feels especially natural in everyday speech.

Is halten a separable verb here? What about anhalten?

In Wir halten uns an die Regel, halten is not separable.
The structure is:

Verb: halten
Reflexive pronoun: uns
Preposition: an
Object: die Regel

So an here is a preposition, not a verb prefix.

There is also a separable verb anhalten, which means:

to stop (e.g. a car, a machine)
to last / to continue (in some uses)

Examples with anhalten (separable):

Der Bus hält an. – The bus stops.
Halte bitte kurz an. – Please stop briefly.

That is different from sich an etwas halten:

Wir halten uns an die Regel. – We stick to the rule.
Der Bus hält an. – The bus stops.

So in your sentence, halten is just a normal verb plus a prepositional phrase, not a separable verb with an-.

Why is uns placed right after halten? Could it go somewhere else in the sentence?

In main clauses, unstressed pronouns like mich, dich, sich, uns, euch usually come as early as possible, right after the conjugated verb (or after another pronoun).

Basic pattern:

Subj – Verb – (reflexive pronoun) – (other elements)

So you get:

Wir halten uns an die Regel.

Typical variations in main clauses:

Wir halten uns immer an die Regel.
Wir halten uns in solchen Situationen an die Regel.

Putting uns later is either wrong or sounds very strange:

✗ Wir halten an die Regel uns. – incorrect/unidiomatic.

In subordinate clauses, the verb goes to the end, and the pronoun goes before other longer elements:

… weil wir uns an die Regel halten.

In the perfect tense, the reflexive pronoun stays close to the auxiliary verb:

Wir haben uns an die Regel gehalten.
Wir hätten uns an die Regel halten sollen.

How would this sentence change with different subjects (I, you, he, they, etc.)?

Here’s the full paradigm of sich an die Regel halten in the present tense:

ich halte mich an die Regel – I stick to the rule
du hältst dich an die Regel – you (sg., informal) stick to the rule
er/sie/es hält sich an die Regel – he/she/it sticks to the rule
wir halten uns an die Regel – we stick to the rule
ihr haltet euch an die Regel – you (pl., informal) stick to the rule
sie halten sich an die Regel – they stick to the rule
Sie halten sich an die Regel – you (formal) stick to the rule

Notice:

halten changes its stem vowel (a → ä) in du and er/sie/es:
- du hältst, er hält
The reflexive pronoun changes with the person: mich, dich, sich, uns, euch, sich.

How do I say We stick to the rules / the plan / the agreement using the same structure?

You can replace die Regel with other nouns, still using sich an + Akkusativ halten:

Wir halten uns an die Regeln. – We stick to the rules.
Wir halten uns an den Plan. – We stick to the plan.
Wir halten uns an die Vereinbarung. – We stick to the agreement.
Wir halten uns an den Vertrag. – We stick to the contract.
Wir halten uns an den Zeitplan. – We stick to the schedule.
Wir halten uns an die Abmachung. – We stick to the arrangement/deal.

Always:

sich an + Akkusativ (an die Regeln, an den Plan, an den Vertrag, …)

Can sich an etwas halten also mean physically holding on to something or someone?

No. For physically holding on to something or someone, German normally uses sich an etwas / jemandem festhalten:

Halt dich am Geländer fest. – Hold on to the railing.
Das Kind hält sich an der Mutter fest. – The child is holding on to its mother.

By contrast, sich an etwas halten (without fest) is about rules, plans, instructions, agreements, etc.:

Halte dich an die Regeln! – Stick to the rules!
Wir halten uns an die Vereinbarung. – We keep to the agreement.

So:

sich an etwas halten → follow / stick to (rule, plan, etc.)
sich an etwas festhalten → physically hold on to (railing, person, object)