1. Chasan/wedding:[1]

A Chasan is obligated to wear Tefillin during Sheva Brachos, just like on any other day of the year.

If the wedding meal continued past daybreak: In the event that the wedding celebration continued until morning [and plans to continue until past the time of Shema] then in previous times the Chasan, his Shushvinin, as well as all the members of the Chuppah, were exempt during the feast from the Mitzvah of Tefillin and Davening, although they remained obligated to read Shema without Tefillin.[2] However, in today’s times, some Poskim[3] rule that the Chasan and his celebrants are not to exempt themselves from prayer, and when they stop to Daven they are also to wear Tefillin.[4] Other Poskim[5] however rule that the Chasan and Shushvinin and all the members of the Chuppah who are partaking in the feast are exempt from even Kerias Shema, and it goes without saying that they are exempt from Davening and Tefillin even today.[6] This applies so long as the Chasan is present with them and is participating in the feast.[7] Practically, the custom is like the former opinion, to stop for Davening and wear Tefillin during the Davening.[8] Nevertheless, despite the custom, one who is lenient like the latter opinion does not lose out.[9] Therefore, in the summer months in which at times the wedding celebration continues until the morning, they are all exempt from all the above Mitzvos so long as the Chasan is still present celebrating with them.

[1] Admur 38:6; Michaber 38:7; Sukkah 25b

[2] The reason: They are exempt from Tefillin being that drunkenness and follies are commonly found by the wedding meal. Now, although they are obligated to read Shema, they are to read it without Tefillin. They are likewise exempt from Davening being that due to their over joyous state of mind they are unable to concentrate on the prayer. They are nevertheless obligated to read Shema being that Bedieved concentration is only required for the first verse, and it is an easy task to focus the mind to concentrate on the first verse. They are therefore obligated to recite the first verse with concentration while the remainder they may say without concentration. [Admur ibid; M”A 38:7]

[3] 1^st opinion in Admur ibid; Rama in Teshuvah 132:1; Terumos Hadeshen 7

[4] The reason: Today, being that we anyways do not have much concentration during prayer irrelevant of the wedding joy, therefore the Chasan and his celebrants are not to exempt themselves from prayer due to lack of concentration. They are therefore also to wear Tefillin upon stopping to Daven, as since they are stopping the feast and they stand and Daven they therefore have no more need to worry of lightheadedness during the prayer [and hence have no reason not to wear Tefillin during the prayer]. However in the previous generations, being that they did not stop the feast in order to daven and would read Shema during the feast, they were exempt from Tefillin being that they may come to lightheadedness while wearing them, being that lightheadedness is common during a feast. [Admur ibid]

[5] 2^nd opinion in Admur ibid; Michaber 38:7; Rashi Sukkah 26a

[6] The reason: As they are all considered to be involved in a Mitzvah and are thus exempt from all other Mitzvos, including Kerias Shema. [ibid]

[7] The reason: As only then is it considered a Mitzvah. [ibid]

[8] Admur ibid; Rama in Teshuvah 132:1; Olas Tamis 38:8; M”B 38:23

[9] Admur ibid; M”A 38:7

[10] Piskeiy Teshuvos 38:7

[11] So is clearly learned from the above Halacha which exempts the entire group of wedding participants from Tefillin due the fact that drunkenness is common.