Imaam Abu Haneefah (rahima-hullaah) said:

((When a hadeeth is found to be saheeh, then that is my madhhab)).

Ibn 'Aabideen in al-Haashiyah (1/63) and in his essay Rasm al-Mufti (1/4 from the Compilation of the Essays of Ibn 'Aabideen), Shaikh Saalih al-Fulaani in Eeqaaz al-Himam (p. 62) and others. Ibn 'Aabideen quoted from Sharh al-Hidaayah by Ibn al-Shahnah al-Kabeer, the teacher of Ibn al-Humaam.

Ref: Fatwa-Online

Shaykh Abdul-Muhsin al-`Ubaykaan said:

"Do you not see that if a man enters a non-Muslim country and is given a pact of safety (a visa), that this is a betrayal?"

Ref: Terrorist with a Visa