Is there a fatwa regarding a person who abandons prayer entering the mosque?

It is permissible for someone who abandons prayer to enter the mosque. It is better to encourage and motivate them to pray, explaining its importance and the danger of abandoning it. This is not negated by the view that they are disbelievers, because the more preponderant opinion is that it is permissible for non-believers to enter mosques other than al-Masjid al-Haram. This is supported by the fact that Thumamah ibn Uthal, while still a polytheist, was tied in the Prophet's Mosque.