Complex sentence: In the 1990s, air marshals were considered to have the highest firearms qualification standards of all United States federal law enforcement agencies and still so have the highest firearms qualifications of all federal law enforcement.
Split into simpler sentences: In the 1990s, air marshals were considered to have the highest firearms qualification standards of all United States federal law enforcement agencies. Currently, Federal Marshals still have the highest firearms qualifications of all federal law enforcement.