Black Tech (Black Techology) is the term that refers to a set of technology and science that is forbidden in Guilty Gear.
In the 21st century, the urgency to preserve the environment became critical, and forced scientists to discover alternate methods of advancement. With the discovery of magic in 2010, mainstream science began to be taken over by magical science. Eventually, mainstream technology was banned by the UN and the term "Black Tech" was coined. The IPF became in charge in regulating technology and people who are selling, using or owning Black Tech is penalized. It's also illegal to spread knowledge about Black Tech. The only exception to this policy is the nation of Zepp.
The entirety of the technological ban is unknown but guns are included, it is also observable in the story the absence of automobiles. Technologies such as satellites, airships and telecommunication devices are still widely used. In the Guilty Gear X Drama CD, a drunk Axl who mentioned the E=MC^2 was almost arrested by the police.