What is legal and what is legitimate are often confused.
There appears to be a distinction within political thinking with regards to the US/British invasion of Iraq, which is considered to be legal but not legitimate.
Legitimate requires the concensus approval of the majority of the public, whereas Legal conforms to Judicial or Statutory Law.
When Politicians carry out an illegitimate act, they suffer the disapproval of the electorate but not the wrath of the Justice System.
It is legal as long as it does not contravene any statutory laws. Apparently the British & US Forces were acting in self-defence against Iraq, which is considered legal.
A similar view is taken of a child that is conceived or born to unmarried parents. It is considered by a concensus view to be illegitimate or not legitimate, but it is not illegal.
Same sex marriages are now legal, but still seen by many as not legitimate.
Abortion is now legal but still seen by many as not a legitimate action.
Legal is the state of being lawfully correct.
Legitimate is the state of being morally correct.