Learn Portuguese (Portugal): Têm-se de impor as sanções rigorosamente. - The sanctions have to be strictly imposed.

This is the passive se construction. The phrase as sanções is actually the grammatical subject of the sentence, not the direct object. Because the subject is plural, the conjugated modal verb ter must also be plural (têm) to agree with it.

Why is the pronoun -se attached to Têm and not to the main verb impor?

In a verbal periphrasis (a conjugated auxiliary verb plus an infinitive, like ter de impor), the pronoun normally attaches to the conjugated verb. Since this is an affirmative sentence with no negative words or other triggers to pull the pronoun to the front, it attaches to the end of Têm.

Does the pronoun -se always go before the preposition de in expressions like ter de?

Yes, when you attach a pronoun to the auxiliary verb in a structure like ter de, it naturally slots between the verb and the preposition. This gives us the somewhat surprising but perfectly correct order of verb + pronoun + preposition + infinitive (Têm-se de impor).

Why does the sentence use ter de instead of ter que to mean have to?

In European Portuguese, ter de is the grammatically correct choice for expressing a strong obligation or duty. Ter que is traditionally reserved for when you have something to do (like having emails that you must read), though native speakers do sometimes mix them up in fast, informal speech.