Members of congress have frequently proposed a constitutional amendment to make flag burning a crime because

The only way to overturn the Supreme Court's ruling that flag burning is protected speech is through a constitutional amendment.

Explanation:

Flag Desecration Amendment was brought proposed in June 27, 2006 but it failed. It is a proposed law to amend the Bill of Rights that would allow the U.S congress to prohibit dishonouring of the of the flag of the US and punish those who are  involved in any such act.

The debate over  protecting it as a national symbol and considering its physical desecration as the freedom of speech is still going on. If the amendment gets ratified it would prohibit all forms o flag dishonouring.

The supreme court has ruled in several cases that due to the First Amendment of the US constitution flag desecration cannot be prohibited by federal,municipal or state government.

on june 23, 1972, the president signed title ix of the education amendments of 1972, 20 u.s.c. into law. title ix is a comprehensive federal law that prohibits discrimination on the basis of sex in any federally funded education program or activity.