How does Germany ban foreign far-right extremists?

Germany is considering banning Austrian far-right extremist Martin Sellner from entering the country. Such a move is not unprecedented, but the legal hurdles are high in the EU.

source https://www.dw.com/en/how-does-germany-ban-foreign-far-right-extremists/a-68129558?maca=en-rss-en-ger-1023-rdf