Member States should also remain free to fix the
provisions of procedure concerning the registration, the
revocation and the invalidity of trade marks acquired by
registration. They can, for example, determine the form
of trade mark registration and invalidity procedures,
decide whether earlier rights should be invoked either
in the registration procedure or in the invalidity
procedure or in both and, if they allow earlier rights to
be invoked in the registration procedure, have an oppo
sition procedure or an
ex officio
examination procedure or
both. Member States should remain free to determine the
effects of revocation or invalidity of trade marks