On the 1st of January 2008 a new rule was put into place by the R&A and USGA outlawing drivers that over use the 'spring effect' or 'trampoline effect'.
Appendix II, 4c of the 2008 edition of the R&A Rules of Golf states that:
"The design, material and/or construction of, or any treatment to, the clubhead (which includes the face) must not … have the effect of a spring which exceeds the limit set forth in the Pendulum Test Protocol on file with the R&A"
This is a new Rule which applies to all golfers of all ability and in all forms of play.
Since the announcement of this new Rule in August 2002, golfers have been encouraged to check the conformance status of their driver, and any driver they may buy in the future, in preparation for its introduction. Many drivers which were previously conforming have now become non-conforming as a result of the new Rule.