(6) Nothing in sub-clause (g) of the said clause shall affect the operation of any existing law in so far as it imposes, or prevent the State from making any law imposing, in the interests of the general public, reasonable restrictions on the exercise of the right conferred by the said sub-clause, and, in particular, 1 [nothing in the said sub-clause shall affect the operation of any existing law in so far as it relates to, or prevent the State from making any law relating to,— (i) the professional or technical qualifications necessary for practising any profession or carrying on any occupation, trade or business, or (ii) the carrying on by the State, or by a corporation owned or controlled by the State, of any trade, business, industry or service, whether to the exclusion, complete or partial, of citizens or otherwise.] 20. Protection in respect of conviction for offences.—(1) No person shall be convicted of any offence except for violation of a law in force at the time of the commission of the Act charged as an offence, nor be subjected to a penalty greater than that which might have been inflicted under the law in force at the time of the commission of the offence. (2) No person shall be prosecuted and punished for the same offence more than once. (3) No person accused of any offence shall be compelled to be a witness against himself. 21. Protection of life and personal liberty.—No person shall be deprived of his life or personal liberty except according to procedure established by law. 2 [21A. Right to education.—The State shall provide free and compulsory education to all children of the age of six to fourteen years in such manner as the State may, by law, determine.] 22. Protection against arrest and detention in certain cases.—(1) No person who is arrested shall be detained in custody without being informed, as soon as may be, of the grounds for such arrest nor shall he be denied the right to consult, and to be defended by, a legal practitioner of his choice. 1. Subs. by the Constitution (First Amendment) Act, 1951, s. 3, for certain words (w.e.f. 18 6-1951). 2 Ins. by the Constitution (Eighty-sixth Amendment) Act, 2002, s. 2 (w.e.f. 1-4-2010). 42