A Day of Rest

Canon 1248 of the Pio-Benedictine Code of Canon Law says:

On feast days of precept, Mass is to be heard; there is an abstinence from servile work, legal acts, and likewise, unless there is a special indult or legitimate customs provide otherwise, from public trade, shopping, and other public buying and selling.

Now that does not say anything about Sundays. The previous canon states:

§ 1. Feast days under precept in the whole Church are only: All and every [Sunday], the feast of the Nativity, Circumcision, Epiphany, Ascension, and the most holy Body of Christ, Immaculate Conception, and Assumption of Mary the Mother of God, of Saint Joseph her spouse, of the Blessed Apostles Peter and Paul, and of All the Saints.

I wonder whether Sunday rest is mandated elsewhere in the Code, or whether it was so well known and assumed that no legislation was necessary. The online Catholic Encyclopedia, published the same year that the Pio-Benedictine Code was promulgated, seems to indicate that the Church at that time did require that Sunday be a day of rest :
"From the eight century the law began to be formulated as it exists at the present day, and the local councils forbade servile work, public buying and selling, pleading in the law courts, and the public and solemn taking of oaths."

The law is not so specific these days as it was, but I think I'm going to avoid shopping on Sundays, as a way of observing the Lord's day and allowing others to rest.