De kan ikke garantere sikkerheten.

From this sentence alone, you cannot be completely sure.

Why:

• De is capitalized because it is the first word in the sentence.
• But De can also be the old-fashioned/formal written form of you in Bokmål.

So the possibilities are:

• de = they
• De = formal/polite you

At the start of a sentence, both appear as De. You need context to know which one is meant.

In modern Norwegian, the polite De is much less common than it used to be, so they is often the more likely reading unless the situation is very formal.

Because kan is the finite verb, and in a normal Norwegian main clause, ikke usually comes after the finite verb.

A very common pattern is:

• subject + finite verb + ikke + infinitive/direct object

So here:

• De = subject
• kan = finite verb
• ikke = negation
• garantere = infinitive
• sikkerheten = object

That gives:

• De kan ikke garantere sikkerheten.

This word order is one of the most important patterns in Norwegian.

After a modal verb such as kan, skal, vil, må, or bør, the next verb is normally in the infinitive without å.

So:

• kan garantere = correct
• kan å garantere = not correct here

This is similar to English:

• can guarantee not
• can to guarantee

Because only one verb in the clause is conjugated as the finite verb, and here that verb is kan.

After kan, the main action verb stays in the infinitive:

• kan garantere

Compare:

• De garanterer sikkerheten. = here garanterer is the finite verb
• De kan garantere sikkerheten. = here kan is the finite verb, so garantere stays infinitive

In Norwegian, definiteness is often built into the noun itself as an ending.

So:

• sikkerhet = safety / security
• sikkerheten = the safety / the security

The ending -en is the definite ending here.

This is very common in Norwegian:

• bok = book
• boken/boka = the book

So there is no separate word for the in this sentence because it is attached to the noun.

Norwegian often uses the definite form where English might use either:

• the safety or simply
• safety

So sikkerheten can sound completely natural even if English would not always say the safety in the same context.

The definite form suggests the safety/security involved in this specific situation, not just the general idea as an abstract concept.

It can mean either, depending on context.

Common possibilities:

• safety = protection from danger, harm, accidents
• security = protection against threats, intrusion, attack, risk

So sikkerheten could mean:

• physical safety
• data security
• public security
• passenger safety and so on

You choose the best English wording from the wider context.

Yes, sikkerheten is the direct object, and garantere does not need a preposition here.

Structure:

• garantere noe = guarantee something

So:

• garantere sikkerheten = guarantee the safety/security

This is similar to English, where guarantee can also take a direct object directly.

This is Bokmål.

The clearest clue is ikke, which is the Bokmål form of not.

In Nynorsk, you would normally expect:

• ikkje instead of ikke

Also, if De here means they, Nynorsk would normally use dei.

So the spelling strongly points to Bokmål.

Yes, it sounds fairly neutral-to-formal.

The verb garantere is common in:

• official notices
• warning labels
• legal or technical language
• customer service statements
• product or service disclaimers

So a sentence like De kan ikke garantere sikkerheten. sounds very natural in formal or institutional contexts. It is not strange Norwegian at all.