First of all, members of Parliament have to do part of the verification. Second, the names must be submitted to the House Administration, and the House security services must have the means to ensure that the people who are invited won't cause this kind of problem.
Then, when the intention is to pay tribute to a guest, the verification should be even more thorough. As a former parliamentarian, I think there is no greater tribute to be received in the House of Commons than to be recognized and introduced by the Speaker. In that respect, the Speaker of the House must ensure that the person being introduced and honoured isn’t the type of person we’re talking about today.