Sefer Ha’mitzvos Ha’Katzar (The concise book of mitzvos)
By the Chofetz Chaim
This book lists the Torah mitzvos that can be observed today
First Section – the Positive Commandments
46. It is a positive commandment for a woman whose husband dies without any children to remove the shoe of her husband's brother that refuses to marry her
As it states in Devarim (Deuteronomy) 25:7-9, "If a man chooses not to marry his brother's widow... she is to remove his shoe from his foot." The order of Chalitza (process of removing the shoe) should only be performed in front of learned rabbaim that are experts in this matter. Any man that does not allow his brother's widow to remove his shoe has disobeyed this positive commandment. There are men who refuse to allow their brother's widow to perform chalitzah, saying that this will be a danger for them. This is a great error! The ways of G-d are straight and no danger will happen if one fulfills a commandment. On the contrary, if a person does not fulfill a positive commandment, it is a great sin.
This applies in all places and at all times.