Maybe. It depends on the "crime" and who was doing it. If it was a fellow worker you should have gone through the chain of command instead of calling the police. Calling the police was not the proper action. If you were being robbed, then calling the police would have been the proper action. Since you were fired my guess is that it was something between you and a person you work with.
Yes, its blatantly against the law in many ways and you should NEVER do it. It is known as 'Impersonation of a Police Officer.'
No, if you have committed a crime, it's not illegal. If you haven't, you shouldn't bother.
Yes, it is certainly illegal in normal circumstances. There might be some situations, such as holding someone who has committed a crime until the police arrive, where it would not be illegal. Otherwise, it would be considered wrongful imprisonment.
Simply, call the police. If he is there against your will, it is illegal.
People cannot be illegal. If you want to report illegal activity, contact the police.
If you haven't committed any illegal acts there is nothing to charge you with.
Take the juvenile into custody.
If you're the police, no. It may be against policy, but it's not, technically speaking, illegal.
A police crime is where the police abuse their power (state organised crime), occupational crime corruption. It is referred to as Trusted white collar crime. The history of police crime is long and varied, involving violations of constitutional rights excessive use of force and related illegal acts to fulfill department objectives both state and federal. Whereas crimes committed by police are acts against people, abuse murder and assault. they are related to personal injury.
Yes, it is illegal for police to solicit a trespass.
if the person is illegal in the country
Yes. It is very much illegal. It is considered the same as discriminating against homosexuals. Not that the internet is governed very well. If you or someone you know is a victim of discrimination please contact your local police.