could a person respond to advertiesements such as the assassination ones with intent to kill the person who would be looking for an assassin but not give any warning whatsoever?

What?

Not sure if I fully understand your question, but...

Yes, you may kill the person advertising for an assassin without warning him or her. Dealing in the business of death is a risky one, and those hiring should be just as weary as they will find that they've acquired many new enemies.

Of course, you'd need to know who the person is.

ok thanks for the answer and sorry if it was not very clear i was not sure how to word it.