In the 1990s, after a report from RSA Data Security, Inc., who were in a licensing dispute with regard to use of the RSA algorithm in PGP, the Customs Service started a criminal investigation of Phil Zimmermann, for allegedly violating the Arms Export Control Act. The US Government had long regarded cryptographic software as a munition, and thus subject to arms trafficking export controls. At that time, the boundary between permitted ("low-strength") cryptography and impermissible ("high-strength") cryptography placed PGP well on the too-strong-to-export side (this boundary has since been relaxed). The investigation lasted three years, but was finally dropped without filing charges.