Thank you everyone for your responses. So can a lapsed Catholic receive communion at another congregation, if it is an open-communion church? (I understand that if it is the closed communion church, you'd have to first convert to that church's denomination).
The defection option is no longer available today as I understand.
A Catholic can receive communion at a Protestant denomination but not licitly. Most protestant denominations do not have valid priests which means they do not have holy Eucharist and that means their holy communion is invalid. I found this on a web page (the page is
here):
According to the Code of Canon Law, receiving communion in a Protestant church is generally not permissible. According to canon 844, “Catholic ministers may licitly administer the sacraments to Catholic members of the Christian faithful only and, likewise, the latter may licitly receive the sacraments only from Catholic ministers.” The key term here is licit. If a Catholic receives communion from a Protestant minister, it is generally considered “illicit” or unlawful.
The reason for the Catholic Church’s general rule against sharing in the Eucharist with other churches is that a person can only be in full communion with one church. As a Catholic, the core of one’s union with Christ is union with the church. The centre of this union lies in the reception of the sacrament of the Eucharist during Mass, which is both a confession and embodiment of unity with the Roman Catholic Church.
But canon 844 includes an exception to the rule “whenever necessity requires or general spiritual advantage suggests, and provided that the danger of error or indifferentism is avoided.” [Canon 844 says more than thie quoted portion, it goes on to say "Christ's faithful for whom it is physically or morally impossible to approach a Catholic minister, may lawfully receive the sacraments of penance, the Eucharist and anointing of the sick from non-Catholic ministers in whose Churches these sacraments are valid."]
The Second Vatican Council’s Decree on Ecumenism said that, as a general rule, common worship and eucharistic and other sacramental sharing should “signify the unity of the church.” But it acknowledges that such sharing can also be seen as advancing unity. In fact, according to the decree, “the gaining of a needed grace sometimes commends” it.
Still, within the confines of canon law, the exceptions to the rule are rather limited, and receiving communion from [for example] a Lutheran pastor during a wedding would normally be seen as “illicit” for Catholic wedding guests. At the same time, some Catholics would like to, and do, receive communion on these rare occasions.
I think it means No a Catholic should not receive communion in a Protestant church but some do and if they do then they've done so illicitly. I do not know if that means that they sinned, but it probably does and then they'd want to confess the sin and refrain from doing it again.