There never was an FCC rule that stated an antenna couldn't be more than 20' tall. If you read the FCC part 95 rules it states that an antenna can not be more than 20' above a structure or more than 60' from the ground to the top. It wasn't illegal to use an aluminum antenna. In 1983 antenna companies just couldn't sell omni directional antennas to non commercial operators anymore. CBers became non commercial operators once licenses were no longer mandated by the FCC shortly before that. Hams can buy them as they are licensed. Other metal antennas can still be sold such as beams. The ruling only applied to omnis and since they were the best sellers many antenna companies went out of business. After the ruling some companies sell them as 10-12 meter antennas which of course includes 11 meters. They just can't state they will work on 11 meters.