Samson attended his own wedding celebration:
וַיֵּ֥רֶד אָבִ֖יהוּ אֶל־הָֽאִשָּׁ֑ה וַיַּ֨עַשׂ שָׁ֤ם שִׁמְשׁוֹן֙ מִשְׁתֶּ֔ה כִּ֛י כֵּ֥ן יַעֲשׂ֖וּ הַבַּחוּרִֽים׃ So his father came down to the woman, and Samson made a feast there, as young men used to do.
The word Mishteh means that wine was present - Rashi on Esther 5:4 writes:
אֶל הַמִּשְׁתֶּה. כָּל סְעוּדָה נִקְרֵאת עַל שֵׁם הַיַּיִן שֶׁהוּא עִיקָר: "To the משתה" – any feast is called after the wine, which is the primary part.
But, per the Rambam, a Nazir, rabbinically, cannot attend a feast with wine. He must instead remain far away. Rambam, Laws of Nazir, 5:10:
מִדִּבְרֵי סוֹפְרִים שֶׁאָסוּר לְנָזִיר לַעֲמֹד בְּמוֹשַׁב שׁוֹתֵי יַיִן וְיִתְרַחֵק מִמֶּנּוּ הַרְבֵּה שֶׁהֲרֵי מִכְשׁוֹל לְפָנָיו. אָמְרוּ חֲכָמִים סָבִיב לַכֶּרֶם לֹא יִקְרַב: According to Rabbinic decree, it is forbidden for a nazirite to abide amidst a gathering of people drinking wine. [Instead,] he should separate himself far from them, because they present a hurdle for him. Our Sages said: "Do not come close [even to] the area around the vineyard."
What strengthens the question is that Samson, while on route to his wedding was scrupulous to avoid entering a vineyard due to the very same rabbinic prohibition - Malbim, Judges 14:10:
ובבואם במשעול הכרמים עקם שמשון את הדרך כענין סחור סחור אמרינן לנזירא לכרמא לא תקרב and when they came to a vineyard pathway, Samson changed his direction a la "Do not come close [even to] the area around the vineyard."
Why then did Samson the Nazir attend his own Philistine-attended wine drinking, wedding banquet?