. 248; McCabe v. Ry. Co., 235 U.S. 151; Davis Mfg. Co. v. Los Angeles, 189 U.S. 207. Furthermore, it is probable that those teachers who have availed themselves of the law, and taken out permits, have waived the right to question the constitutionality of the legislation. The issuance of a permit, which is in the nature of a license, is mandatory on the Department, if the applicant has complied with the prescribed conditions, In re Kalama, 22 Haw. 96; Tai Kee v. Minister of Interior, 11 Haw. 57; and if in such case a permit should be refused, the applicant could either compel its issuance by mandamus or else proceed with immunity to act as if he had a permit, Territory v. Kua, 22 Haw. 307; Royall v. Virginia, 116 U.S. 572. No permit can be revoked without giving the holder an opportunity to be heard, Wilson v. Lord-Young Eng. Co., 21 Haw. 87; and, even if the provisions as to permits and pledges were invalid, that would not affect the validity of the remaining portions of these Acts. Territory v. Apa, 28 Haw. 222. Teachers of American citizens in this extensive system of schools should know at least the elements of the history, institutions, ideals and language of the country in which they are teaching and of which their pupils are citizens.

The State contends that the lower court erred in failing to sever the term "to loiter about" from HRS § 445-43, thereby leaving the remainder of the statute to stand as constitutional. The general rule of law concerning the concept of severability is that if any part of a statute is held invalid, and if the remainder is complete in itself and is capable of being executed in accordance with the apparent legislative intent, then the remainder must be upheld as constitutional. Territory v. Tam, 36 Haw. 32 (1942); Territory v. Apa, 28 Haw. 222 (1925). It is not necessary, however, to deal with the issue of severability because we find that the entire statute is violative of equal protection guarantees in that it no longer bears a rational relationship to the harm sought to be avoided.

Laws 1947, Act 115, § 7. In re Atcherley, 19 Haw. 535, 543. (See also Territory v. Hoy Chong, 21 Haw. 39, 43; Ter. v. Apa, 28 Haw. 222, 227; Hawaiian Trust Co. v. Smith, 31 Haw. 196, 202; Damon v. Tsutsui, 31 Haw. 678, 697; Territory v. Tam, 36 Haw. 32, 38.) Decree reversed, with leave to complainant to amend.

This court has, upon several occasions, considered the legal effect of partial invalidity of a statute. (See Boyd v. Auditor, 15 Haw. 361, 364; Territory v. Cunha, 15 Haw. 607, 609; Robinson v. Baldwin, 19 Haw. 9, 13; In re Atcherley, 19 Haw. 535, 543; Territory v. Hoy Chong, 21 Haw. 39, 43; Ter. v. Apa, 28 Haw. 222, 227; Hawaiian Trust Co. v. Smith, 31 Haw. 196, 202.) Much that was said in In re Atcherley, supra, is applicable here, including the citation from Cooley.

" Hawaiian Trust Co. v. Smith, 31 Haw. 196, 202. To the same effect is Territory v. Apa, 28 Haw. 222, 227. "If, after striking out the unconstitutional part of a statute, the residue is intelligible, complete and capable of execution, it will be upheld and enforced, except, of course, in cases where it is apparent that the rejected part was an inducement to the adoption of the remainder." Territory v. Hoy Chong, 21 Haw. 39, 43. The clause relating to proof of vested rights is severable from the rest of the section.