Vetar
 

How can I say in English?
Le vetaré mi habitación ( context. Talking about a cat so that it doesn´t leave any of its hairs on my clothes)

I´ll veto my room to it/him. I want to use the word veto, not ban or prohibit.

I'll veto access to my room by him (the cat).
I'll veto his (the cat's) rights to my room.
Permission to my room by him (the cat) will be vetoed.

It would be much more natural to use ban.

You should also note that veto is a word often used in official capacities. A proposal was vetoed by the senate, for example.

Vetoing a cat's access seems comical, but if you propose to allow pets to the co-op board, they may veto it.

Under ordinary circumstances, you will more likely hear, I won't allow the cat in my room.

I just noticed PJT33's response which I completely agree with.

I know but I wanted to use veto, metaphorically.

One of the meanings of 'veto' fits what you intended to say, hence my examples. However, as others have said, 'veto' isn't commonly used to portray that idea.

In UK you'd say "I'll stop that cat from coming into my room".

Well, I just wanted to know the use of Veto, in Spanish is not very usual either, but people would understand it.