Question: Saint Regis is a hamlet at the confluence of the St. Regis River and a seaway which legally includes what canal?

Context paragraphs:
Saint Regis Canoe Area: The Saint Regis Canoe Area in Adirondack Park is the largest wilderness canoe area in the Northeastern United States and the only designated canoe area in New York state.  It is closed to motorized vehicles.  Among the 58 ponds (small lakes) and lakes are Upper Saint Regis Lake, part of the Seven Carries route, and Saint Regis Pond.  It contains the headwaters of the West and Middle Branch of the Saint Regis and the Saranac Rivers. Only two of the lakes can be reached without a portage, or "carry" as it's known in the region.  Primitive canoe camping is permitted on many of the lakes and ponds.  Saint Regis Mountain and Long Pond Mountain are within the area.

Hogansburg, New York: Hogansburg is a hamlet, in Franklin County, in the town of Bombay in New York state, United States.  It lies on NY 37 near the Canadian-US border at the confluence of the St. Regis River with the Saint Lawrence Seaway.  Hogansburg borders the St. Regis Mohawk Reservation.

Lower St. Regis Lake: 350 acre Lower St. Regis Lake is a part of the St. Regis River in the Adirondacks in northern New York State.  At its northern edge is Paul Smith's College, former site of Paul Smith's Hotel.  Along with Upper St. Regis Lake and Spitfire Lake, it became famous in the late 19th century as a summer playground of America's power elite, drawn to the area by its scenic beauty and by the rustic charms of Paul Smith's Hotel.  It is the site of a small chapel, originally built of logs, St. John's in the Wilderness, that was formerly attended by well-dressed families that arrived in canoes, rowboats and sailboats.

St. Regis Lakes: St. Regis Lake is the name of two lakes on the St. Regis River in the Adirondacks in northern New York state: Upper St. Regis Lake and Lower St. Regis Lake.  Saint Regis Pond is to the west, in the Saint Regis Canoe Area.

St. Regis River (Montana): The St. Regis River is an approximately 32.5 mi tributary of the Clark Fork of the Columbia River in Montana in the United States.  It begins at Lookout Pass on the Idaho/Montana border, flows east and ends at the confluence with the Clark Fork in the city of St. Regis.  Its drainage is 330 sqmi .  The record high flow for the St. Regis River in Montana was recorded on May 19, 1954 at 11,000 cubic feet per second according to USGS gaging data.

Saint Regis Pond: Saint Regis Pond is a 400 acre pond, the largest in the Saint Regis Canoe Area in the Adirondacks in northern New York state.  It drains into the west branch of the St. Regis River.  It is the centerpiece of the "Seven Carries" canoe route.

Saint Lawrence Seaway: The Saint Lawrence Seaway (French: "la Voie Maritime du Saint-Laurent" ) is a system of locks, canals and channels in Canada and the United States that permit ocean-going vessels to travel from the Atlantic Ocean to the Great Lakes of North America, as far inland as the western end of Lake Superior.  The Seaway is named for the Saint Lawrence River, which flows from Lake Ontario to the Atlantic Ocean.  Legally, the Seaway extends from Montreal, Quebec, to Lake Erie and includes the Welland Canal.

Keese Mill, New York: Keese Mill is a hamlet west of Paul Smiths, New York in Franklin County, New York in the Adirondacks.  It is named for a sawmill that was located on the Keese Mill dam on the Saint Regis River.  Keese Mills road, which starts at Paul Smiths, is the only road in the hamlet; it provides access to Black Pond and Long Pond, trails to Saint Regis and Jenkins Mountains and the Saint Regis Esker Trail, and the middle branch of the Saint Regis River.

St. Regis River: The St. Regis River is an 86 mi river in northern New York in the United States.  It flows into the Saint Lawrence River at the hamlet of St Regis in the St. Regis Mohawk Reservation.  The Saint Regis River basin includes Upper and Lower St. Regis Lakes, and Saint Regis Pond in the Saint Regis Canoe Area.

Saint Regis, New York: Saint Regis is a hamlet in the St. Regis Mohawk Reservation in Franklin County, New York, United States.  It lies on the NY 37 highway near the Canada–United States border, at the confluence of the St. Regis River with the Saint Lawrence Seaway.

Supporting paragraphs: Saint Regis, New York Saint Lawrence Seaway
Answer: Welland Canal