Jumuah in Dar al-Kufr
There are many countries that are deemed to be Dar al-Kufr, as they do not rule with the laws of Allah completely. In such countries, a Muslim may ask himself whether Jumuah prayer must still be prayed or not.
The Jumuah prayer is obligatory for every adult male Muslim. Yes, this is both obligatory in Dar al-Islam as well as in Dar al-Kufr.
Majority of the Imams of the past, are of the opinion that Jumuah is obligatory regardless. Some held the opinion Jumuah prayer is only obligatory in Dar al-Islam, but this opinion is not correct.
قُلْتُ لِأَحْمَدَ قَالَ ابْنُ الْمُبَارَكِ: إِذَا كَانَ تُقَامُ الْحُدُودُ فِي مَوْضِعَيْنِ مِثْلِ بَغْدَادَ، فَلَا بَأْسَ بِهِ، قَالَ: هُوَ يَذْهَبُ فِي هَذَا إِلَى قَوْلِ أَصْحَابِ الرَّأْيِ، يَقُولُونَ «الْجُمُعَةُ فِي الْمَوْضِعِ الَّذِي تُقَامُ فِيهِ الْحُدُودُ»
مِعْتُ أَحْمَدَ، يَقُولُ: أَيُّ حَدٍّ كَانَ يُقَامُ بِالْمَدِينَةِ؟ قَدَّمَهَا مُصْعَبُ بْنُ عُمَيْرٍ، وَهُمْ مُخْتَبِئُونَ فِي دَارٍ فَجَمَعَ بِهِمْ، وَهُمْ أَرْبَعُونَ.
[مسائل الإمام أحمد رواية أبي داود السجستاني - المجلد 1 - الصفحة 83]
Abu Dawud told Imam Ahmad that Ibn al-Mubarak said that the Jumuah prayer must only be estabilished in a place that is ruled with the laws of Allah, whereupon Imam Ahmad replied: "He shares this opinion with Ahl Raiyy (Abu Hanifa and his followers). They say that Jumuah prayer is only estabilished in a place that is ruled with the laws of Allah." Imam Ahmad then went on to say: "Which law of Allah was held in Madinah (before Hijrah)? The Jumuah was still prayed by Mus'ab ibn 'Umayr and other among the Muslims, while they prayed it in a house, and they were with forty." [Masail Abu Dawud 1/83]
أخبرنا عبد الرزاق قال: أخبرنا معمر عن الزهري قال:
ابعث رسول الله صلى الله عليه وسلم مصعب بن عمير بن هاشم (4) إلى أهل المدينة ليقرئهم القرآن، فاستأذن رسول الله صلى الله عليه وسلم أن يجمع بهم فأذن له رسول الله صلى الله عليه وسلم، وليس يومئذ بأمير، ولكنه انطلق يعلم أهل المدينة
[المصنف - عبد الرزاق الصنعاني - 5146]
Al-Zuhri said: "The Messenger of Allah (ﷺ) sent Mus'ab ibn 'Umayr to the people of Madinah to teach them the Quran. He sought the Messenger of Allah's permission to gather them for the Friday Prayer and the Messenger of Allah (peace and blessings of Allah be upon him) allowed him. At that time, Mus'ab ibn 'Umayr was not the one in authority but he had gone (only) to teach the people of Madinah." [Musannaf Abdurrazaaq #5146]
This is also proof that the Imam of Jumuah prayer does not have to be an authority figure in order for it to be valid.
Now, there may not always be an oppurtunity to pray Jumuah prayer in Dar al-Kufr. Maybe the conditions of Jumuah prayer cannot be met, like not having 40 Muslims praying it, or you cannot attend it because it is too far.
If the conditions of the obligatory Jumuah cannot be met, then there will be no blame upon the Muslim in Dar al-Kufr.