1) Arrest means placing a person under lawful detention against their will for the purposes of law enforcement. When is it fair to arrest someone? Individuals have a right to liberty, and it has been held by the courts that if the police do not adequately respect rights to liberty by ensuring that (i) they have some evidence to justify the arrest before it takes place, (ii) that they tell the person why they are being arrested and (iii) that they release the person as soon as possible, then the arrest becomes unlawful. This was the position in a case called Christie v. Leachinsky [1947] A.C. 573.
Where it was said that "a citizen...is prima facie entitled to personal freedom...". But, the right to liberty is not absolute, and its balance with other societal interests (which are reflective of other rights) can be demonstrated by Article 5 of the European Convention on Human Rights and Fundamental Freedoms (which becomes part of UK law under the Human rights Act 1998):
European Convention on Human Rights (Cmd. 8969, 1950) Art . 5.1
"Everyone has the right to liberty and security of person. No one shall be deprived of his liberty save in the following cases and in accordance with a procedure prescribed by law...
(c) The lawful arrest or detention of a person effected for the purpose of bringing him before the competent legal authority on reasonable suspicion of having committed an offence or when it is reasonably considered necessary to prevent his committing an offence or fleeing after having done so..."
(2) The most regulated powers of arrest are those which are allowed under warrant. A warrant is a formal legal document which authorises someone to take action. In this case, warrants can be issued by any individual magistrate to a police officer to carry out the arrest of a named individual. This is the common method of proceeding against people who have failed to pay their fines after a conviction, or have failed to "answer bail" ie appear at court or a