The verse "The punishment of those who wage war against Allah and His Apostle, and strive with might and main for mischief through the land is execution, or crucifixion, or the cutting off of hands and feet from opposite side or exile from the land...most merciful" was revealed about polytheists. If any of them repents before they are arrested, it does not prevent from inflicting on him the prescribed punishment which he deserves.  

{ إِنَّمَا جَزَاءُ الَّذِينَ يُحَارِبُونَ اللَّهَ وَرَسُولَهُ وَيَسْعَوْنَ فِي الأَرْضِ فَسَادًا أَنْ يُقَتَّلُوا أَوْ يُصَلَّبُوا أَوْ تُقَطَّعَ أَيْدِيهِمْ وَأَرْجُلُهُمْ مِنْ خِلاَفٍ أَوْ يُنْفَوْا مِنَ الأَرْضِ } إِلَى قَوْلِهِ { غَفُورٌ رَحِيمٌ } نَزَلَتْ هَذِهِ الآيَةُ فِي الْمُشْرِكِينَ فَمَنْ تَابَ مِنْهُمْ قَبْلَ أَنْ يُقْدَرَ عَلَيْهِ لَمْ يَمْنَعْهُ ذَلِكَ أَنْ يُقَامَ فِيهِ الْحَدُّ الَّذِي أَصَابَهُ  

Concerning the statement of Allah, the Most High: The recompense of those who wage war against Allah and His Messenger. "This Verse was revealed concerning the idolators. Whoever among them repents before he is captured, you have no way against him. This Verse does not apply to the Muslims. Whoever kills, spreads mischief in the land, and wages war against Allah and His Messenger, then joins the disbelievers before he can be caught, there is nothing to prevent the Hadd punishment being carried out on him because of what he did." (Using translation from Nasāʾī 4046)  

عَنِ ابْنِ عَبَّاسٍ فِي قَوْلِهِ تَعَالَى {إِنَّمَا جَزَاءُ الَّذِينَ يُحَارِبُونَ اللهَ وَرَسُولَهُ} [المائدة 33] الْآيَةَ قَالَ نَزَلَتْ هَذِهِ الْآيَةُ فِي الْمُشْرِكِينَ فَمَنْ تَابَ مِنْهُمْ قَبْلَ أَنْ يُقْدَرَ عَلَيْهِ لَمْ يَكُنْ عَلَيْهِ سَبِيلٌ وَلَيْسَتْ هَذِهِ الْآيَةُ لِلرَّجُلِ الْمُسْلِمِ فَمَنْ قَتَلَ وَأَفْسَدَ فِي الْأَرْضِ وَحَارَبَ اللهَ وَرَسُولَهُ ثُمَّ لَحِقَ بِالْكُفَّارِ قَبْلَ أَنْ يُقْدَرَ عَلَيْهِ لَمْ يَمْنَعْهُ ذَلِكَ أَنْ يُقَامَ فِيهِ الْحَدُّ الَّذِي أَصَابَ